One way to fake it would be to turn a spotlight upwards for the effect and use the blend setting to make the outside softer. The light fixture itself can be a slight emitter so it appears to have light pass through it, or you could set another light inside to pass through a translucent material or one that has SSS added to it. Another way would be to use a texture for the light, and yet another is to use a renderer that takes IES light information for correct shape and falloff of light depending on the fixture type and so on. Usually this data can be found by searching for photometrics.
Of course remember to add an inverse square falloff. This is how lights (electromagnetic energy in general) works.
Quick mock up with very little attention to material details just as a proof of concept:
This example uses the upturned spot light with a low to mid-range blend, a point light, area light for the overall lighting, some translucentcy and SSS. Of course it is rushed, so it’s not great quality, but the important part is the cone and its falloff.
There are many ways to achieve the effect that you are looking for with their strengths and weaknesses, it comes down to what you want to do and the desired effect you want.
Thanks very much, that’s just what i was after, do you think you could upload the blend file? How do you change falloff? and what purpose does SSS fulfil in this example? Sorry for all the questions, i know almost nothing about blender apart from some polygonal modelling.
One thing to keep in mind is … “fake it,” in this context at least, “is entirely normal.”
When you are looking to create “this-or-that physical effect” in Blender, remember that “physical reality actually has nothing at all to do with it.” You can, in fact, spend an inordinate amount of time trying your best to “mimic what is actually happening in ‘The Real World,’” and, even if you somehow do manage to achieve such a thing, only wind up with something that is (a) very slow to render, and(b) not very satisfactory.
So… practice the notion of “looking at the light.” Figure out what the light is actually doing, no matter why the light would be doing such a thing in the real world. Create a fast-and-efficient computer model (“there’s more than one way to do it …”) that reasonably achieves that.
Hollywood built a slew of “main street Texas towns” that were (literally) “only skin deep,” because they knew that the sets would never, ever be viewed from any other angle. (They determined this, also, before they built them.) You should do the same. Figure out, in advance, not only what the effect ought to look like, but exactly under what conditions it will actually be viewed. Then, build the effect accordingly.
Yes… that requires you to make more-or-less every creative decision “in advance.”
Lots of folks try it the other way: they try to create “the real world, in all its glory,” before they decide whether/how/if it will be used in whatever-it-is they are trying to build. And that’s like a set-designer building a real town and then telling the director, “okay, I’ve built the thing … now, do you know yet where you want to put the camera?”
Here is the blend. I didn’t save the original, but this was slapped together quickly to show you the concept. The part that would most interest you would be the spot light and the blend amount. Just play around and see what you come up with. Ask more questions if you are stuck. If you really want to see the influence, I would turn off or mark as not renderable, the other lights, so you can just focus on that one in particular.